Data commit

Task/Modular-inverse/IS-BASIC/modular-inverse.basic

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+100 PRINT MODINV(42,2017)
+120 DEF MODINV(A,B)
+130   LET B=ABS(B)
+140   IF A<0 THEN LET A=B-MOD(-A,B)
+150   LET T=0:LET NT=1:LET R=B:LET NR=MOD(A,B)
+160   DO WHILE NR<>0
+170     LET Q=INT(R/NR)
+180     LET TMP=NT:LET NT=T-Q*NT:LET T=TMP
+190     LET TMP=NR:LET NR=R-Q*NR:LET R=TMP
+200   LOOP
+210   IF R>1 THEN
+220     LET MODINV=-1
+230   ELSE IF T<0 THEN
+240     LET MODINV=T+B
+250   ELSE
+260     LET MODINV=T
+270   END IF
+280 END DEF